CA1214196A - Color rendition high pressure sodium arc tubes having an oxygen getter - Google Patents
Color rendition high pressure sodium arc tubes having an oxygen getterInfo
- Publication number
- CA1214196A CA1214196A CA000446261A CA446261A CA1214196A CA 1214196 A CA1214196 A CA 1214196A CA 000446261 A CA000446261 A CA 000446261A CA 446261 A CA446261 A CA 446261A CA 1214196 A CA1214196 A CA 1214196A
- Authority
- CA
- Canada
- Prior art keywords
- oxygen getter
- arc tube
- color rendition
- high pressure
- oxygen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/24—Means for obtaining or maintaining the desired pressure within the vessel
- H01J61/26—Means for absorbing or adsorbing gas, e.g. by gettering; Means for preventing blackening of the envelope
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/82—Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr
- H01J61/825—High-pressure sodium lamps
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- Discharge Lamp (AREA)
- Vessels And Coating Films For Discharge Lamps (AREA)
Abstract
IMPROVED COLOR RENDITION HIGH PRESSURE
SODIUM ARC TUBES HAVING AN OXYGEN GETTER
ABSTRACT OF THE DISCLOSURE
A high pressure sodium lamp having improved color rendition is disclosed. The improved color rendition high pressure sodium lamp has an inner arc tube having a pair of thermionic electrodes at least one of which has affixed a metallic oxygen getter. The oxygen getter maintains the desired color rendition over the life of the high pressure sodium lamp.
SODIUM ARC TUBES HAVING AN OXYGEN GETTER
ABSTRACT OF THE DISCLOSURE
A high pressure sodium lamp having improved color rendition is disclosed. The improved color rendition high pressure sodium lamp has an inner arc tube having a pair of thermionic electrodes at least one of which has affixed a metallic oxygen getter. The oxygen getter maintains the desired color rendition over the life of the high pressure sodium lamp.
Description
~ 1 ~ LD 9038 IMPROVED COLOR R~NDITION ~IGH PRESSURE
SODIUM ARC TUBES ~AVING AN OXYGEN ~ET ER
BACRGROUND OF T~E INVE~TION
This invention relates to a high pres~ure ~odlum vapor lamp compri~ing an alumina ceramic inner envelope, and more particularly, the invention relates to a high pre~sure ~odium vapor lamp wherein an inner arc tube is provided wl~h a pair of ~hermionie electrod~s at least one of which has affixed there~o an oxygen getter which malntain~ the ~olor rendition of the lamp.
~igh pres~ure ~odium vapor lamps have ~cund wide~pread u~e duri~g the past decade for commercial lighting applicatio~s, e~pecially outdoor lighting~
Such lamps are des~rlbed in W~SO Patent No7 3,248,590 =
Schmidt, High Pressure Sodium Yapor Lamp~, ~igh pressure sodium lamps typically oomprise a slender tubular inner envelope of a light transmissive refractory oxide material res.istant to sodium at high temperatures, and suitably ~ormed of a high density polycrystalline aluminaO The c~ramic ~rc tube i~
~ generally ~upported wi~hin an outer vi~reous enve~ope or jacket provided at one end with the u~ual ~crew base. ~he electrodes of khe inner envelope are conn~cted to terminal~ of the base~ tbat i~ to the .
.
.. . ___.. _ _ .. .. .
SODIUM ARC TUBES ~AVING AN OXYGEN ~ET ER
BACRGROUND OF T~E INVE~TION
This invention relates to a high pres~ure ~odlum vapor lamp compri~ing an alumina ceramic inner envelope, and more particularly, the invention relates to a high pre~sure ~odium vapor lamp wherein an inner arc tube is provided wl~h a pair of ~hermionie electrod~s at least one of which has affixed there~o an oxygen getter which malntain~ the ~olor rendition of the lamp.
~igh pres~ure ~odium vapor lamps have ~cund wide~pread u~e duri~g the past decade for commercial lighting applicatio~s, e~pecially outdoor lighting~
Such lamps are des~rlbed in W~SO Patent No7 3,248,590 =
Schmidt, High Pressure Sodium Yapor Lamp~, ~igh pressure sodium lamps typically oomprise a slender tubular inner envelope of a light transmissive refractory oxide material res.istant to sodium at high temperatures, and suitably ~ormed of a high density polycrystalline aluminaO The c~ramic ~rc tube i~
~ generally ~upported wi~hin an outer vi~reous enve~ope or jacket provided at one end with the u~ual ~crew base. ~he electrodes of khe inner envelope are conn~cted to terminal~ of the base~ tbat i~ to the .
.
.. . ___.. _ _ .. .. .
- 2 - LD 9038 shell and center contacts of such base. The space between the inner and outer envelopes is typically evacuated in order to conserve heat.
The color rendition of standard high pressure sodium (HPS) lamps may be improved by increasing the internal sodium partial pressure within -the arc chamber of the inner envelope formed of the polycrystalline alumina. An improved color rendition of standard EIPS
lamps may necessitate that the polycrystalline alumina arc chamber be opera-ted with two to three times the internal sodium partial pressure relative to conventional standard lamps. In addition, for such increased sodium pressure the wall temperature between the elctrode tips wi-thin the arc chamber may be increased by 100C relative to the standard HPS lamp in order to offset the reduction of luminous efficacy which normally accompanies operation at increased sodium pressure. An improved color rendition high pressure sodium lamp operated at iwo to three times typical sodium pressure is described in Canadian Patent Application Serial Number 440,974, Strok, filed November 10, 1983 and assigned to the assignee of the present invention~
High sodium pressures for HPS lamps are typically developed by increasing the operating temperature of the sodium-mercury amalgam reservoir typically located and thermally connected to one of -the thermionic electrodes within the arc tube. As is well known in the HPS lamp art, at sodium pressures within the arc tube of two to three times higher than those for arc tubes of standard color HPS lamps, the additional pressure broadens the sodium resonance lin~ and continuum radiations at blue and green wavelengths which effectively increases the Correlated Color Temperature several hundred degrees Kelvin, and the ~ ...-~,
The color rendition of standard high pressure sodium (HPS) lamps may be improved by increasing the internal sodium partial pressure within -the arc chamber of the inner envelope formed of the polycrystalline alumina. An improved color rendition of standard EIPS
lamps may necessitate that the polycrystalline alumina arc chamber be opera-ted with two to three times the internal sodium partial pressure relative to conventional standard lamps. In addition, for such increased sodium pressure the wall temperature between the elctrode tips wi-thin the arc chamber may be increased by 100C relative to the standard HPS lamp in order to offset the reduction of luminous efficacy which normally accompanies operation at increased sodium pressure. An improved color rendition high pressure sodium lamp operated at iwo to three times typical sodium pressure is described in Canadian Patent Application Serial Number 440,974, Strok, filed November 10, 1983 and assigned to the assignee of the present invention~
High sodium pressures for HPS lamps are typically developed by increasing the operating temperature of the sodium-mercury amalgam reservoir typically located and thermally connected to one of -the thermionic electrodes within the arc tube. As is well known in the HPS lamp art, at sodium pressures within the arc tube of two to three times higher than those for arc tubes of standard color HPS lamps, the additional pressure broadens the sodium resonance lin~ and continuum radiations at blue and green wavelengths which effectively increases the Correlated Color Temperature several hundred degrees Kelvin, and the ~ ...-~,
- 3 - LD 9038 Color Rendition Index of the HPS lamp is thereby desirably increased up to a range of between 60 to ~5.
~ he arc tubes of color improved ~PS lamps may ho~t undesirable s~dium losses caused by chemical reactions from oxygen sources within the arc tube created by impuritie-c undesirably introduced into the arc tube during the manufacturing process of the color improYed ~PS lamps. These undesirable impurities typically have undesirable results on lamp performance as manifested by an increased voltage of the arc tube, r~du~ed luminous efficacy of the ~PS lamp, and color shiEt toward the red portion of the visible electromagnetic spectrum over the life of the lamp. The color shift toward red is particularly disadvantageous when the ~PS
lamp is used in oolor~sensi ive interior commercial and industrial applications, Further, it has been empirically determined that improved color HPS lamps exhibit greater color ~hifts, primarily related ~o red ~pectral content than standard lamps or the same amount of ~odium loss due to internal chemi~al reac~ions.
Undesired chemical reactions rela~ed to ~PS lamp arc tubes are further described in UOS. Patent 3,48~343 of P. J. Jorgensen, issued December 23, 1969. U.S. Patent 3,485,343 describes the reaction of sodium with small amounts of oxygen and water which may be present in an arc tube, which, in turn, promotes reaction with the alumina of the arc tube resul~ing in an undesirable eemoval of free sodium from the interioE
of the arc tube, U.SO Patent 3l485,343 further describes ~he use of an oxygen getter ~ormed from doping a metal with from about 2~ to 2D~ by weight of a ca~ivn me~al having a plu~ four valence such as a 90~
yttrium, 10~ thorium alloy. The yt~rium thorium alloy oxygen getter is a relatively e~pensive material. It ~ 4 hD 9038 is considered desired that an oxygen getter of a relatively inexpensive material be provided so that the unde~irable chemical reactions that affect the desired color rendi~ion ~ay be elimina~ed in a relativ ly S inexpensive ma~nerO
Accordingly, an object of the preRent invention is to provide mean~ for improving the color rendition of the ~PS lamps ~uch that color shift thereof typically caused by undesirable chemical reaction~ between the sodium dose and oxygen ~ources undesirably contained within the arc tubes ~hereof i~ reduced, A further object of the pre~ent invention is to provide means for reducing the undesired chemical reactions for the improved color ~P5 lamps Quch ~hat a desired Color Rendition Inde~ remains substantially constant over the life of such lampsO
These and other object~ of the present invention will become apparent upon consideration of the following description of the inventionO
S~MM~RY QF T~E INVENTI0~
This invention is directed to improved color rendition high pre~sure sodium lamps having an o~y~en getter for reducing ~he sodium lo ses typically created within the arc tubes of such lampsO
~5 Accordingly, in one embodiment of the present invention, an improved color rendition high pre~sure metal vapor lamp comprising an ou~er va~reous envelope and an arc ~ube con~ained within the ou~er envelope.
The arc tube has sealed ~herein a pair of ~hermaonic 30 electrodesO The ~EC ube contain~ a charge of vaporizable metal havin~ a sodium partial pressure in ~he range o approximately 100 to ~00 ~orr and xenon gas in the raD~e of approximately 10 to 400 . orr~ The arc ~ube fur~her has an oxy~en getter which is a~fixed 35 to at least one o~ he ~hermionic ele~trodes~ The ..
~ 5 LD 9038 oxygen getter is a m~tal selected from the group of zirconium, vanadium~ titanium, yttrium, and thorium metals and alloys thereof excluding yttrium, The present inven~ion may best be described by reference to the following description of the drawing and ~he detailed description of the preferred embodiments 3 BRIEF DESCRIPTION OF THE DRAWINGS
~I~. 1 is a front elevation view of a high lD pressure sodium vapor di~charge lamp according to the present invention~
FIG. 2 is an exposed sectional view, in a slightly enlarged manner, of the arc tube of ~IG. 1 in accordance with one embodiment of ~he present inventionO
FIG. 3 is an exposed sectional view, in a slightly enlarged manner, of the arc tube of FIG. 1 showing another embodiment of the present invention.
FIG. 4 is a high pressure sodium (~PS) lamp partially broken away so as to show a.double wire arc 20 tubeO
FIG. 5 is an exposed s~ctional view of the arc tube of the ~PS lamp of FXG. 4.
~ IG. 6 is an International Commission on Illumination (I~C.I~) chromaticity diagram ~howing a 25 typical improvement of the color temperature of the ~PS
lamp realized by the present invention.
DETA:l:LED DESCRIPTIO~ OF T E_PREFERRED EMBODIMENTS
A high pres~ure sodium vapor lamp 10 embodying the present invention and corresponding to a ~onventional 30 250 wa t ~iæe lamp is illustrated in ~IG. 1. A high pressure sodium (HPS) vapor lamp generally compri~es a vitreous outer envelope 12 wikh a ~tandard mogul screw base 13 attached to the stem end which is shown uppermost in EI~o 1~ A reentrant stem press 14 35 ~upports a pair of relativel~ heavy lead-in conductors ~z~
~ 6 ~ LD ~038 lS and 16 e~ten~ing through the stem 14 and having outer ends connected to the screw shell 17 and eyelets 18 of the baseO
The HPS lamp 10 includes an inner envelope or arc tube 19 centrally ~ocated within the outer envelope 12. The arc tube 19 i~ comprised of a length of light-transmissive ceramic ormed of a polycrystalline alumina ceramic which is translucent. The arc tube 19 contains a charge of vaporizable metals having a sodium 10 partial pressure in the range of approximately 100 to 400 torr and a xenon gas in the range ~f approximately 19 to 400 torrO
The upper end of the arc tube 19 is clo~ed by an alumina ceramic sealing plug ~0 through which e~ nds 15 hermetically a niobium inlead 21 which ~upport~ an upp~r electrode tsh~wn more clearly in FIGS. 2 and 3 to be described) within the ~rc tube 19. Similarly, the lower end of the ar~ tube 19 has a clo~ure whieh comprises a ceramic ~eali~ plug 22 through which 20 e~tends a thin walled niobium tube 23. The ceramic sealing plugs 20 and 22 are de cribed in greater detail in ~,S, Patent 4,065,691 M~Vey; Ceramic Lamp~ ~aving Electrode Supported by Crimped Tubular Inlead. The niobium tube 23 serves both as an inlead for arc ~ube ~5 19 and as a reservoir for storin~ e~ces~ alkali metal and mercury contained within ~he arc tube 190 ~he shank of the lower electrode tshown in FIGS. 2 and 3 -to be described) of arc tube 19 projects into reservoir tube 23 and is locked in place by crimping the niobium 30 re~rvoir tube about the lower electrode at location 24 as shown in F~G. 1~
The aro tube 19 of ~PS lamp 10 of ~0 1 and a double wire arc tube ~2 of a ~PS lamp 6~ sf FIG. 4 bo~h to be deseribed hereina~er, are of substantial 35 interest in respect to the present inventiQnO ~ore ( $~., ~ 7 ~ LD 9038 particularly, for one Pmbodiment of the present invention the arrangement of oxygen getters 40 and 42 about the electrode shanks 48 and 50 enclosed within arc tube 19 is of particular interest to the present invention and ~uch an arrangement i5 shown in FIG~ 2.
FIG. 2 shows an exposed sectional view~ in a ~lightly enlarged manner relative to the arc tube 1~ of FIG. 1, of the arc tube 19, Electrodes 44 and 46 each comprise a low work function emissive material such as dibarium calcium tungstate which is formed intv the windings wrapped about the elec~rode shanks 48 and 50 re~pectivelyO
~ IG. ~ further ~hows oxygen getters 40 ~nd 4~ of the present invention as being wrapped around electrode shanks ~8 and S0, respectively. ~lthough FI~ 2 ~hows each cf the electrode shanks 48 and 50 a having arranged oxygen getters 40 and 42, it should be noted that in accordance with the prac~ice of this invention only one oxygen ~etter 40 or 42 need be arranged with ei~her electrode 44 or 46, ~ he oxygen ge~ters 40 and 42 re pre~erably formed of a single 2irconium (Zr) metal, although other ~ingle metals such as vanadium, titaniumt yttrium or thoriu~
are al80 applicable, ~urther, oxygen getters 40 and 42 may also ~e an alloy formed from combinations of the zirconium, vana~ium, titanium and ~horium me~als, The oxygen getters 40 and 42 formed vf selected metals chemically react wi~h oxygen gas sources during lamp operation to prevent oxygen reaction with sodium in ~he ~odium-mercury amalgamO
The oxygen getters 40 and 42 are shown in FIGo 2 in a wire wrapped manner about el~otrode sha~ks 48 and 50, ~he oxygen ge~ters 40 and 4~ can alternaSively be placed around elec~rode shanks 4B and ~0, re~pecSively~
in a ~heet lik~ form, ~ 8 LD 9038 A second embodiment of the present invention is shown in FIG. 3D FIGo 3 i8 similar to that shown for FIG. 2 and uses the ame ref~rence numbers where applicable. The difference bstween FIG. 2 and FIG. 3 is that the oxygen getter related to the electrode ~hank 50 is located within the niobium reservoir tube 23 and has the reference number 52 as shown in YI~. 3.
Although not shown in FIG, 3, the practice of this invention contemplates the placement of an oxygen yetter within the niobium reservoir ~ube 23 and on each of the electrode ~hanks 48 and 50. ~he oxygen getter 52 can be inserted into the niobium reservoir tube 23 in a wire-like form or roll sheet form.
A further embodiment of the present invention is a related double;~wire inner arc tube 62 centrally located within a BPS lapp 60 of FIG. 4 and supported r in part, by support memb~r 63~ ~he double-wire arc tube 62 is ~hown by means of~a partially exposed illustra~ion of the ~PS lamp 60 of FIG~ 40 The ~PS lamp 60 is of type LU35 or LU50 commercially available ~rom the ~igh Intensity and ~uartz Lighting Department of the General Electric Company, The double-wire arc tube 62 is shown more clearly in FIG. 50 FIG. 5 shows the arc tube S2, preferably formed ~f a polycrystalline alumina, as having two oppositely located inleads 64 and 7~ formed of niobium wire, The inlead 78 passes through and is supported ~y sealing plug 800 The i~ner portion of inlead 78 labeled 82 is connected to a ~han~ 86 by a but~ wel~
340 The inner portion 82 of inlead 78 i~ a niobium feedthrough for arc tube 62, The shank 86 is formed of a tungsten ma~erial and ha~ elec~rode c9il~ 88 having an emission mix b~tween its turns~ The emission mix can be of a dibarium calcium tung~tate materi~l. .
; 35 The inlead 64 passe~ through and is suppor~ed by a fi ~ 9 LD 9038 ceramic sealing plug 660 The inner portion of inlead 64 labeled 68 is connected to ~ ~hank 72 by a butt weld 70, The inner portion 6B of inlead 64 is a niobium feedthrough for arc tube 62. The shank 72 is formed of tungsten and has electrode coils 74 similar to the electrode coils ~8.
FIG. 5 shows an oxygen getter 76 wrapped around the niobium feedthrough 68 and shank 72. Although not shown in FI~o 50 an o~ygen getter may also be wrapped around the niobium feedthrough 82 and shank 86 both related to the niobium inlead 780 The oxygen get~er 7S
is of the same metal previously described for oxygen getters 40, 42 and 52.
In order that She present invent~o~ may be fully appre~iated, re~erence i~ now made to comparative ~est data obtained ~etween ~PS lamps having improved but progressively decaying color rendition and ~PS lamp S0 of FIGo 4 having the double wire arc tube 62 o FIG, 5 of the pres~nt invention which has an improved color rendition ~aintained by the oxygen getters of the presenS invention, A total o~ 20 color improved 35 watt ~PS arc tubes of double wire design wer~ constructed and ~es~ed in accor~dance with the practice o this invention, The arc tube chambers of t~e 20 ~PS lamps had an inner diameter of 405 mm and an ar~-gap, tha~ is~ the spacing between the thermionic electrodes/ of 12,0 mm. The (20) color improved 35 watt ~PS arc tubes were dosed with 10 milligrams of 25~ by weight sodium-mercury amalgam a xenon starting gas ~t a pressure of 15 torr at room tempera~ureO The hermionic ele~rodes of ~he 20 arc Subes were ac~iYa~ed with a dibarium calcium tungstate ~o as to improve the ~hermionic emission of the electrodes, The group of 20 HPS lamps were then divided into ~welve (12) ~PS lamps 60 according to th~
~z~
~ 10 ~ LD 9038 present invention having oxygen getters 76 and eight (B) ~PS lamps not having an oxygen getter~
Two oxygen getters 76 for eacb of the twelve (12) ~PS lamps 60 of the present invention were formed by a 5 single turn of 0.020~ zirconium wire and each oxygen getter 76 was wrapped abou~ the base of each electrode ~hank in a manner ~imilar to that shown in ~IG. 5 for oxygen getter 75 and located between the electrode coils 74 and B8 and ceramic end plug ~6 and 80. The group of twelve (12) aro tubes 62 of the present invention and the ei~ht (8) arc tubes not having the advantages of the presant invention w~re made into finished lamps and then photometered. All wenty (20) of the fi~ished lamps ha~ an initial Correlated Color Temperature of approximately 2200K and a Color Rendition Index of 75O
All 20 ~PS lamps were operated for a total of 500 hours at an operating wa~age of 35 watts~ The resul~s of the 500 hours of operation of the t~enty (20) HPS
lamps are best described with reference to FIG. 60 FI~. 6 is a portion of he International Commission on Illumination (IoCoI~ ) chromaticity diagram well known in the ~PS lamp art. The X axis shown in FIG. fi with locations of 04~0t 0O500~ 0O510, 0.520 and 0.530, and the Y axis of FIGo 6 with lo-cations 0.400, 0.410, 0O420~ 0~430 and 0O440 form a coordinate system by which changes in lamp Correlated Color Temperature over a duration of time may be illustratedO FIG. 6 ~hows a eurve 90 represen~ative of an ideal black body such a~ ~ub~tantially achievable from an incandescent l~gh~ source~ FIG. 6 show~ this black body curve 90 a~ intersec~ed by a plurali~y of Correlated Color T~mperature lines of ~000~, 2065Kr 2200OK~ 2230K~ 2400R and 2600K, 3~ The 20 ~PS lamp~ before being ~ubject to the 500 ,~
ll LD 9038 hours of testing had an initial Correlat~d Color Temperature of approximately ~200K, a color rendition index of 75/ ~nd a location 92 shown in PIG, 6. Location 92 of FIG. 6 is located along ~he 2~00g Correlated Color Temperature line and at a position just below but very near he ideal black body curve gO, ~ fter ~ubjecting the 20 ~PS lamps to ~he 500 hours of testing, the twelve (12) improved color rendition lamps 60 of the present invention were determined to be advantag~ously shifted from the Correlated Color Temperature of location 92 to ~ Correlated Color Temperature of location 94, and conversely, the eight (8) color improved ~PS lamps not having the oxygen getter 76 of the presen~ invention were determined ~o l~ have an undesir~ble ~hift downw~rd in Correlated Color Temperature from location 92 to location 96, both of FI5. 6. The unde~irable shift of the BPS lamps not having the advantages ~f t~e present invention i8 toward the red por~ion of the visible electromagnetic ~o ~pe~trum, and, conversely~ ~he desirable shift of ~he HPS lamps of the present invention is away rom the red portion of the visible electromagnetic spec~rum. The advantageous shift o the 12 ~PS lamps o the present invention is 3hown, in phantom, in FIG. 6, by an arrow 98~ and, similarly, t~e undesirable shift of the ~PS
lamps not in accordance with the present invention is shown, in phantom, in FIG. 6 by an arrow 1O0D
All of the twelve (12~ ~PS lamps 60 of the present invention and ~he eight ~8~ lamps no~ havin.~ the ~eaching~ of ~he pre~ent inven ion were physically examined after the 5D0 hours of. testing. The twelve ~ PS lamps 60 of the present inven~ion exhibited arc chambers ends that were noticeably cleaner relative to blackened en~s of the ~PS lamp~ which did not embody ; 35 the p.resent lnYen~ion, ~he noticeably cleaner arc ~2.~
- 12 ~ LD 903B
chamber ends of the arc tube 62 of the present invention is beneficial with regard to the efficacy and maintenance of the ~PS lamps 60.
It should now be appreciated that the practice of the present invention provides an improved color ~PS
lamps 60 and 10 having improved maintenance of high color temperature9 The improvement of maintenance of high color temperature is achieved by the oxygen getter of the present invention. It should be noted that although the comparative data was related to 35 watt ~PS lamps, the present invention contemplates HPS lamps having much higher wat~age such as 1000 watts and conversely having much lower wattage such as 15 wattsO
~ he arc tubes of color improved ~PS lamps may ho~t undesirable s~dium losses caused by chemical reactions from oxygen sources within the arc tube created by impuritie-c undesirably introduced into the arc tube during the manufacturing process of the color improYed ~PS lamps. These undesirable impurities typically have undesirable results on lamp performance as manifested by an increased voltage of the arc tube, r~du~ed luminous efficacy of the ~PS lamp, and color shiEt toward the red portion of the visible electromagnetic spectrum over the life of the lamp. The color shift toward red is particularly disadvantageous when the ~PS
lamp is used in oolor~sensi ive interior commercial and industrial applications, Further, it has been empirically determined that improved color HPS lamps exhibit greater color ~hifts, primarily related ~o red ~pectral content than standard lamps or the same amount of ~odium loss due to internal chemi~al reac~ions.
Undesired chemical reactions rela~ed to ~PS lamp arc tubes are further described in UOS. Patent 3,48~343 of P. J. Jorgensen, issued December 23, 1969. U.S. Patent 3,485,343 describes the reaction of sodium with small amounts of oxygen and water which may be present in an arc tube, which, in turn, promotes reaction with the alumina of the arc tube resul~ing in an undesirable eemoval of free sodium from the interioE
of the arc tube, U.SO Patent 3l485,343 further describes ~he use of an oxygen getter ~ormed from doping a metal with from about 2~ to 2D~ by weight of a ca~ivn me~al having a plu~ four valence such as a 90~
yttrium, 10~ thorium alloy. The yt~rium thorium alloy oxygen getter is a relatively e~pensive material. It ~ 4 hD 9038 is considered desired that an oxygen getter of a relatively inexpensive material be provided so that the unde~irable chemical reactions that affect the desired color rendi~ion ~ay be elimina~ed in a relativ ly S inexpensive ma~nerO
Accordingly, an object of the preRent invention is to provide mean~ for improving the color rendition of the ~PS lamps ~uch that color shift thereof typically caused by undesirable chemical reaction~ between the sodium dose and oxygen ~ources undesirably contained within the arc tubes ~hereof i~ reduced, A further object of the pre~ent invention is to provide means for reducing the undesired chemical reactions for the improved color ~P5 lamps Quch ~hat a desired Color Rendition Inde~ remains substantially constant over the life of such lampsO
These and other object~ of the present invention will become apparent upon consideration of the following description of the inventionO
S~MM~RY QF T~E INVENTI0~
This invention is directed to improved color rendition high pre~sure sodium lamps having an o~y~en getter for reducing ~he sodium lo ses typically created within the arc tubes of such lampsO
~5 Accordingly, in one embodiment of the present invention, an improved color rendition high pre~sure metal vapor lamp comprising an ou~er va~reous envelope and an arc ~ube con~ained within the ou~er envelope.
The arc tube has sealed ~herein a pair of ~hermaonic 30 electrodesO The ~EC ube contain~ a charge of vaporizable metal havin~ a sodium partial pressure in ~he range o approximately 100 to ~00 ~orr and xenon gas in the raD~e of approximately 10 to 400 . orr~ The arc ~ube fur~her has an oxy~en getter which is a~fixed 35 to at least one o~ he ~hermionic ele~trodes~ The ..
~ 5 LD 9038 oxygen getter is a m~tal selected from the group of zirconium, vanadium~ titanium, yttrium, and thorium metals and alloys thereof excluding yttrium, The present inven~ion may best be described by reference to the following description of the drawing and ~he detailed description of the preferred embodiments 3 BRIEF DESCRIPTION OF THE DRAWINGS
~I~. 1 is a front elevation view of a high lD pressure sodium vapor di~charge lamp according to the present invention~
FIG. 2 is an exposed sectional view, in a slightly enlarged manner, of the arc tube of ~IG. 1 in accordance with one embodiment of ~he present inventionO
FIG. 3 is an exposed sectional view, in a slightly enlarged manner, of the arc tube of FIG. 1 showing another embodiment of the present invention.
FIG. 4 is a high pressure sodium (~PS) lamp partially broken away so as to show a.double wire arc 20 tubeO
FIG. 5 is an exposed s~ctional view of the arc tube of the ~PS lamp of FXG. 4.
~ IG. 6 is an International Commission on Illumination (I~C.I~) chromaticity diagram ~howing a 25 typical improvement of the color temperature of the ~PS
lamp realized by the present invention.
DETA:l:LED DESCRIPTIO~ OF T E_PREFERRED EMBODIMENTS
A high pres~ure sodium vapor lamp 10 embodying the present invention and corresponding to a ~onventional 30 250 wa t ~iæe lamp is illustrated in ~IG. 1. A high pressure sodium (HPS) vapor lamp generally compri~es a vitreous outer envelope 12 wikh a ~tandard mogul screw base 13 attached to the stem end which is shown uppermost in EI~o 1~ A reentrant stem press 14 35 ~upports a pair of relativel~ heavy lead-in conductors ~z~
~ 6 ~ LD ~038 lS and 16 e~ten~ing through the stem 14 and having outer ends connected to the screw shell 17 and eyelets 18 of the baseO
The HPS lamp 10 includes an inner envelope or arc tube 19 centrally ~ocated within the outer envelope 12. The arc tube 19 i~ comprised of a length of light-transmissive ceramic ormed of a polycrystalline alumina ceramic which is translucent. The arc tube 19 contains a charge of vaporizable metals having a sodium 10 partial pressure in the range of approximately 100 to 400 torr and a xenon gas in the range ~f approximately 19 to 400 torrO
The upper end of the arc tube 19 is clo~ed by an alumina ceramic sealing plug ~0 through which e~ nds 15 hermetically a niobium inlead 21 which ~upport~ an upp~r electrode tsh~wn more clearly in FIGS. 2 and 3 to be described) within the ~rc tube 19. Similarly, the lower end of the ar~ tube 19 has a clo~ure whieh comprises a ceramic ~eali~ plug 22 through which 20 e~tends a thin walled niobium tube 23. The ceramic sealing plugs 20 and 22 are de cribed in greater detail in ~,S, Patent 4,065,691 M~Vey; Ceramic Lamp~ ~aving Electrode Supported by Crimped Tubular Inlead. The niobium tube 23 serves both as an inlead for arc ~ube ~5 19 and as a reservoir for storin~ e~ces~ alkali metal and mercury contained within ~he arc tube 190 ~he shank of the lower electrode tshown in FIGS. 2 and 3 -to be described) of arc tube 19 projects into reservoir tube 23 and is locked in place by crimping the niobium 30 re~rvoir tube about the lower electrode at location 24 as shown in F~G. 1~
The aro tube 19 of ~PS lamp 10 of ~0 1 and a double wire arc tube ~2 of a ~PS lamp 6~ sf FIG. 4 bo~h to be deseribed hereina~er, are of substantial 35 interest in respect to the present inventiQnO ~ore ( $~., ~ 7 ~ LD 9038 particularly, for one Pmbodiment of the present invention the arrangement of oxygen getters 40 and 42 about the electrode shanks 48 and 50 enclosed within arc tube 19 is of particular interest to the present invention and ~uch an arrangement i5 shown in FIG~ 2.
FIG. 2 shows an exposed sectional view~ in a ~lightly enlarged manner relative to the arc tube 1~ of FIG. 1, of the arc tube 19, Electrodes 44 and 46 each comprise a low work function emissive material such as dibarium calcium tungstate which is formed intv the windings wrapped about the elec~rode shanks 48 and 50 re~pectivelyO
~ IG. ~ further ~hows oxygen getters 40 ~nd 4~ of the present invention as being wrapped around electrode shanks ~8 and S0, respectively. ~lthough FI~ 2 ~hows each cf the electrode shanks 48 and 50 a having arranged oxygen getters 40 and 42, it should be noted that in accordance with the prac~ice of this invention only one oxygen ~etter 40 or 42 need be arranged with ei~her electrode 44 or 46, ~ he oxygen ge~ters 40 and 42 re pre~erably formed of a single 2irconium (Zr) metal, although other ~ingle metals such as vanadium, titaniumt yttrium or thoriu~
are al80 applicable, ~urther, oxygen getters 40 and 42 may also ~e an alloy formed from combinations of the zirconium, vana~ium, titanium and ~horium me~als, The oxygen getters 40 and 42 formed vf selected metals chemically react wi~h oxygen gas sources during lamp operation to prevent oxygen reaction with sodium in ~he ~odium-mercury amalgamO
The oxygen getters 40 and 42 are shown in FIGo 2 in a wire wrapped manner about el~otrode sha~ks 48 and 50, ~he oxygen ge~ters 40 and 4~ can alternaSively be placed around elec~rode shanks 4B and ~0, re~pecSively~
in a ~heet lik~ form, ~ 8 LD 9038 A second embodiment of the present invention is shown in FIG. 3D FIGo 3 i8 similar to that shown for FIG. 2 and uses the ame ref~rence numbers where applicable. The difference bstween FIG. 2 and FIG. 3 is that the oxygen getter related to the electrode ~hank 50 is located within the niobium reservoir tube 23 and has the reference number 52 as shown in YI~. 3.
Although not shown in FIG, 3, the practice of this invention contemplates the placement of an oxygen yetter within the niobium reservoir ~ube 23 and on each of the electrode ~hanks 48 and 50. ~he oxygen getter 52 can be inserted into the niobium reservoir tube 23 in a wire-like form or roll sheet form.
A further embodiment of the present invention is a related double;~wire inner arc tube 62 centrally located within a BPS lapp 60 of FIG. 4 and supported r in part, by support memb~r 63~ ~he double-wire arc tube 62 is ~hown by means of~a partially exposed illustra~ion of the ~PS lamp 60 of FIG~ 40 The ~PS lamp 60 is of type LU35 or LU50 commercially available ~rom the ~igh Intensity and ~uartz Lighting Department of the General Electric Company, The double-wire arc tube 62 is shown more clearly in FIG. 50 FIG. 5 shows the arc tube S2, preferably formed ~f a polycrystalline alumina, as having two oppositely located inleads 64 and 7~ formed of niobium wire, The inlead 78 passes through and is supported ~y sealing plug 800 The i~ner portion of inlead 78 labeled 82 is connected to a ~han~ 86 by a but~ wel~
340 The inner portion 82 of inlead 78 i~ a niobium feedthrough for arc tube 62, The shank 86 is formed of a tungsten ma~erial and ha~ elec~rode c9il~ 88 having an emission mix b~tween its turns~ The emission mix can be of a dibarium calcium tung~tate materi~l. .
; 35 The inlead 64 passe~ through and is suppor~ed by a fi ~ 9 LD 9038 ceramic sealing plug 660 The inner portion of inlead 64 labeled 68 is connected to ~ ~hank 72 by a butt weld 70, The inner portion 6B of inlead 64 is a niobium feedthrough for arc tube 62. The shank 72 is formed of tungsten and has electrode coils 74 similar to the electrode coils ~8.
FIG. 5 shows an oxygen getter 76 wrapped around the niobium feedthrough 68 and shank 72. Although not shown in FI~o 50 an o~ygen getter may also be wrapped around the niobium feedthrough 82 and shank 86 both related to the niobium inlead 780 The oxygen get~er 7S
is of the same metal previously described for oxygen getters 40, 42 and 52.
In order that She present invent~o~ may be fully appre~iated, re~erence i~ now made to comparative ~est data obtained ~etween ~PS lamps having improved but progressively decaying color rendition and ~PS lamp S0 of FIGo 4 having the double wire arc tube 62 o FIG, 5 of the pres~nt invention which has an improved color rendition ~aintained by the oxygen getters of the presenS invention, A total o~ 20 color improved 35 watt ~PS arc tubes of double wire design wer~ constructed and ~es~ed in accor~dance with the practice o this invention, The arc tube chambers of t~e 20 ~PS lamps had an inner diameter of 405 mm and an ar~-gap, tha~ is~ the spacing between the thermionic electrodes/ of 12,0 mm. The (20) color improved 35 watt ~PS arc tubes were dosed with 10 milligrams of 25~ by weight sodium-mercury amalgam a xenon starting gas ~t a pressure of 15 torr at room tempera~ureO The hermionic ele~rodes of ~he 20 arc Subes were ac~iYa~ed with a dibarium calcium tungstate ~o as to improve the ~hermionic emission of the electrodes, The group of 20 HPS lamps were then divided into ~welve (12) ~PS lamps 60 according to th~
~z~
~ 10 ~ LD 9038 present invention having oxygen getters 76 and eight (B) ~PS lamps not having an oxygen getter~
Two oxygen getters 76 for eacb of the twelve (12) ~PS lamps 60 of the present invention were formed by a 5 single turn of 0.020~ zirconium wire and each oxygen getter 76 was wrapped abou~ the base of each electrode ~hank in a manner ~imilar to that shown in ~IG. 5 for oxygen getter 75 and located between the electrode coils 74 and B8 and ceramic end plug ~6 and 80. The group of twelve (12) aro tubes 62 of the present invention and the ei~ht (8) arc tubes not having the advantages of the presant invention w~re made into finished lamps and then photometered. All wenty (20) of the fi~ished lamps ha~ an initial Correlated Color Temperature of approximately 2200K and a Color Rendition Index of 75O
All 20 ~PS lamps were operated for a total of 500 hours at an operating wa~age of 35 watts~ The resul~s of the 500 hours of operation of the t~enty (20) HPS
lamps are best described with reference to FIG. 60 FI~. 6 is a portion of he International Commission on Illumination (IoCoI~ ) chromaticity diagram well known in the ~PS lamp art. The X axis shown in FIG. fi with locations of 04~0t 0O500~ 0O510, 0.520 and 0.530, and the Y axis of FIGo 6 with lo-cations 0.400, 0.410, 0O420~ 0~430 and 0O440 form a coordinate system by which changes in lamp Correlated Color Temperature over a duration of time may be illustratedO FIG. 6 ~hows a eurve 90 represen~ative of an ideal black body such a~ ~ub~tantially achievable from an incandescent l~gh~ source~ FIG. 6 show~ this black body curve 90 a~ intersec~ed by a plurali~y of Correlated Color T~mperature lines of ~000~, 2065Kr 2200OK~ 2230K~ 2400R and 2600K, 3~ The 20 ~PS lamp~ before being ~ubject to the 500 ,~
ll LD 9038 hours of testing had an initial Correlat~d Color Temperature of approximately ~200K, a color rendition index of 75/ ~nd a location 92 shown in PIG, 6. Location 92 of FIG. 6 is located along ~he 2~00g Correlated Color Temperature line and at a position just below but very near he ideal black body curve gO, ~ fter ~ubjecting the 20 ~PS lamps to ~he 500 hours of testing, the twelve (12) improved color rendition lamps 60 of the present invention were determined to be advantag~ously shifted from the Correlated Color Temperature of location 92 to ~ Correlated Color Temperature of location 94, and conversely, the eight (8) color improved ~PS lamps not having the oxygen getter 76 of the presen~ invention were determined ~o l~ have an undesir~ble ~hift downw~rd in Correlated Color Temperature from location 92 to location 96, both of FI5. 6. The unde~irable shift of the BPS lamps not having the advantages ~f t~e present invention i8 toward the red por~ion of the visible electromagnetic ~o ~pe~trum, and, conversely~ ~he desirable shift of ~he HPS lamps of the present invention is away rom the red portion of the visible electromagnetic spec~rum. The advantageous shift o the 12 ~PS lamps o the present invention is 3hown, in phantom, in FIG. 6, by an arrow 98~ and, similarly, t~e undesirable shift of the ~PS
lamps not in accordance with the present invention is shown, in phantom, in FIG. 6 by an arrow 1O0D
All of the twelve (12~ ~PS lamps 60 of the present invention and ~he eight ~8~ lamps no~ havin.~ the ~eaching~ of ~he pre~ent inven ion were physically examined after the 5D0 hours of. testing. The twelve ~ PS lamps 60 of the present inven~ion exhibited arc chambers ends that were noticeably cleaner relative to blackened en~s of the ~PS lamp~ which did not embody ; 35 the p.resent lnYen~ion, ~he noticeably cleaner arc ~2.~
- 12 ~ LD 903B
chamber ends of the arc tube 62 of the present invention is beneficial with regard to the efficacy and maintenance of the ~PS lamps 60.
It should now be appreciated that the practice of the present invention provides an improved color ~PS
lamps 60 and 10 having improved maintenance of high color temperature9 The improvement of maintenance of high color temperature is achieved by the oxygen getter of the present invention. It should be noted that although the comparative data was related to 35 watt ~PS lamps, the present invention contemplates HPS lamps having much higher wat~age such as 1000 watts and conversely having much lower wattage such as 15 wattsO
Claims (5)
1. An improved color rendition high pressure metal vapor lamp comprising:
an outer vitreous envelope;
an arc tube contained within the outer envelope and having sealed therein a pair of thermionic electrode structures, said arc tube containing a charge of vaporizable metals having a sodium partial pressure in the range of approximately 100 to 400 torr and a xenon gas in the range of approximately 10 to 400 torr, and an oxygen getter affixed to at least one of said thermionic electrode structures of said arc tube, said oxygen getter consisting of a metal selected from the group of zirconium, vanadium, titanium, yttrium and thorium metals, and alloys thereof excluding yttrium, said oxygen getter in cooperation with the given sodium partial pressure range and xenon gas range effective to reduce undesirable oxygen and sodium chemical reactions within said arc tube so as to maintain the color rendition of said lamp.
an outer vitreous envelope;
an arc tube contained within the outer envelope and having sealed therein a pair of thermionic electrode structures, said arc tube containing a charge of vaporizable metals having a sodium partial pressure in the range of approximately 100 to 400 torr and a xenon gas in the range of approximately 10 to 400 torr, and an oxygen getter affixed to at least one of said thermionic electrode structures of said arc tube, said oxygen getter consisting of a metal selected from the group of zirconium, vanadium, titanium, yttrium and thorium metals, and alloys thereof excluding yttrium, said oxygen getter in cooperation with the given sodium partial pressure range and xenon gas range effective to reduce undesirable oxygen and sodium chemical reactions within said arc tube so as to maintain the color rendition of said lamp.
2. An improved color rendition high pressure vapor lamp according to claim 1 wherein one of said pair of thermionic electrode structures is connected to a tube serving as a reservoir for storing an excess of alkali metal contained within the said arc tube and has disposed therein another oxygen getter being a metal selected from the same group of metals and alloys of said oxygen getter.
3. An improved color rendition high pressure vapor lamp according to claim 1 further comprising an additional oxygen getter affixed to the other thermionic electrode structure of said arc tube, said additional oxygen getter being a metal selected from the same group of metals and alloys of said oxygen getter.
4. An improved color rendition high pressure vapor lamp according to claim 2 further comprising an additional oxygen getter affixed to the other thermionic electrode structure of said arc tube, said additional oxygen getter being a metal selected from the same group of metals and alloys of said oxygen getter.
5. An improved color rendition high pressure vapor lamp according to claim 1 wherein said thermionic electrode structures each further have a niobium inlead extending into said arc tube and provided for connections external to said arc tube, the other thermionic electrode structure of said arc tube having affixed thereto another oxygen getter being of a metal selected from the same group of metals and alloys of said oxygen getter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US46593383A | 1983-02-14 | 1983-02-14 | |
| US465,933 | 1983-02-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1214196A true CA1214196A (en) | 1986-11-18 |
Family
ID=23849758
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000446261A Expired CA1214196A (en) | 1983-02-14 | 1984-01-27 | Color rendition high pressure sodium arc tubes having an oxygen getter |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS59160951A (en) |
| BE (1) | BE898890A (en) |
| CA (1) | CA1214196A (en) |
| DE (1) | DE3404661A1 (en) |
| FR (1) | FR2541043B1 (en) |
| GB (1) | GB2138202A (en) |
| IT (1) | IT1175940B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1222274A (en) * | 1983-03-10 | 1987-05-26 | Philip J. White | Unsaturated vapor high pressure sodium lamp getter mounting |
| CA1241365A (en) * | 1983-03-10 | 1988-08-30 | John A. Scholz | Unsaturated vapor high pressure sodium lamp arc tube fabrication process |
| CA1222273A (en) * | 1983-03-10 | 1987-05-26 | Philip J. White | Unsaturated vapor pressure type high pressure sodium lamp |
| US4620129A (en) * | 1985-04-29 | 1986-10-28 | General Electric Company | Gettered high pressure sodium lamp |
| US5128106A (en) * | 1990-07-12 | 1992-07-07 | Gte Products Corporation | Lamp with an oxygen detector |
| DE19653364C2 (en) * | 1996-12-20 | 2003-01-09 | Erhard Habermann | flash tube |
| ITMI20032208A1 (en) * | 2003-11-14 | 2005-05-15 | Getters Spa | CATODO WITH INTEGRATED AND LOW FUNCTION GETTER WORK FOR COLD CATO LAMPS. |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB698840A (en) * | 1950-09-09 | 1953-10-21 | British Thomson Houston Co Ltd | Improvements in electric incandescent lamps and similar devices |
| US3248590A (en) * | 1963-03-01 | 1966-04-26 | Gen Electric | High pressure sodium vapor lamp |
| GB1211176A (en) * | 1967-02-16 | 1970-11-04 | Gen Electric | High-pressure sodium vapor lamp |
| US3485343A (en) * | 1967-08-28 | 1969-12-23 | Gen Electric | Oxygen getter for high pressure sodium vapor lamp |
| US3558963A (en) * | 1968-08-16 | 1971-01-26 | Gen Electric | High-intensity vapor arc-lamp |
| US3621322A (en) * | 1968-09-12 | 1971-11-16 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | High-pressure compact arc lamp with electrodes containing tantalum carbide |
| GB1514467A (en) * | 1975-05-23 | 1978-06-14 | Wall Colmonoy Ltd | Controlled atmosphere and vacuum processes |
| US4025812A (en) * | 1975-10-14 | 1977-05-24 | General Electric Company | Alumina ceramic alkali metal lamp having metal getter structure |
| GB2125615B (en) * | 1982-08-05 | 1985-11-27 | Emi Plc Thorn | Improvements in hp discharge lamps |
-
1984
- 1984-01-27 CA CA000446261A patent/CA1214196A/en not_active Expired
- 1984-02-03 GB GB08402889A patent/GB2138202A/en not_active Withdrawn
- 1984-02-10 JP JP59022042A patent/JPS59160951A/en active Pending
- 1984-02-10 DE DE19843404661 patent/DE3404661A1/en not_active Withdrawn
- 1984-02-13 BE BE0/212372A patent/BE898890A/en not_active IP Right Cessation
- 1984-02-13 IT IT19588/84A patent/IT1175940B/en active
- 1984-02-13 FR FR8402149A patent/FR2541043B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2138202A (en) | 1984-10-17 |
| FR2541043A1 (en) | 1984-08-17 |
| GB8402889D0 (en) | 1984-03-07 |
| BE898890A (en) | 1984-08-13 |
| DE3404661A1 (en) | 1984-08-16 |
| IT8419588A0 (en) | 1984-02-13 |
| IT1175940B (en) | 1987-08-12 |
| FR2541043B1 (en) | 1987-02-27 |
| JPS59160951A (en) | 1984-09-11 |
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| MKEX | Expiry |